Turbine engines typically include a compressor section that draws air into the engine and compresses the air; a combustor section that mixes the compressed air with fuel and ignites the mixture; and a turbine section that converts molecular energy of the combustion process to rotational energy. It has been recognized that the type of fuel used and the state of the fuel when injected and combusted can affect performance of the turbine engine. For example, it is known that anhydrous ammonia (NH3), when combusted, produces low, if any, carbon emissions. However, to enhance combustion of the ammonia, it must first be vaporized and conditioned (catalytically cracked). And, vaporizing and cracking the ammonia can require complicated equipment and energy levels that reduce the engine's efficiency.
To improve efficiency of the turbine engine, intercooling is commonly employed. Intercooling includes removing energy from the air between compression stages. The energy is conventionally removed by way of an air or water heat exchanger. That is, air that has been compressed during a first stage is directed through the heat exchanger before being compressed further during a second stage. A coolant, either air or water, is directed in counter- or cross-flow direction through the heat exchanger to remove energy from the partially compressed air. By removing energy, the work of compression lessens, and more turbine power is available than would have otherwise been possible without intercooling.
An example of an ammonia fueled, intercooled turbine engine is described in a paper (hereinafter “Lear Paper”) entitled “Ammonia-Fueled Combustion Turbines” by Lear of the University of Florida Department of Mechanical and Aerospace Engineering. In the Lear Paper, an ammonia fueled turbine engine is described that also includes intercooling. However, instead of using conventional fluids (air or water) to cool the partially compressed air, the Lear Paper discloses using the ammonia fuel to cool the air. That is, ammonia is circulated through an intercooler circuit, where the ammonia is expanded, picks up heat from the partially compressed air, condenses, releases the heat, and then is pumped back through the circuit. Before the ammonia condenses and releases the heat, a portion of the hot vaporized ammonia is redirected to a combustor of the engine, where it mixes with already cooled and further-compressed air and is burned to generate power. Because the fuel of the engine is also used to cool the inlet air, the need for a separate cooling fluid may be reduced. And, the heat picked up by the fuel during the intercooling process may enhance combustion of the fuel.
Although the engine disclosed in the Lear Paper may have low emissions and high efficiency due to the use of ammonia for both fueling and cooling, it may still be suboptimal. That is, the intercooling circuit of the Lear Paper requires excess ammonia be available for the intercooling process. More specifically, the intercooling circuit recycles at least some of the ammonia used to cool the inlet air, with only a portion of the ammonia being directed to the combustor. Because some of the ammonia is recycled, it must, itself, be cooled prior to cooling the inlet air. This additional cooling step may result in a more complex, more expensive, and less efficient system. Further, it may be possible that the heat picked up from the intercooling process by the ammonia is insufficient for optimum combustion thereof. That is, the ammonia may still require an additional step of vaporization/cracking before optimal combustion may take place.
The disclosed turbine engine is directed to overcoming one or more of the problems set forth above.